Radon Potential Index
Scientific studies have shown that Radon gas is a known human lung carcinogen.
Prolonged exposure to high levels of Radon gas can cause lung cancer. Millions
of homes and buildings contain high levels of radon gas. The Radon Potential
Index is a result of the combined efforts of the USGS and EPA to ascertain a
radon potential for the US. Important, this index should be used only as
a guide. The only real way in knowing if a home or area has unhealthy levels of
radon is specific testing. The following is a brief summary of the study
performed by the USGS on behalf of the EPA.

Background InformationUranium: The Source

To understand radon gas - where it forms, how it forms, how it moves - we have
to start with its ultimate source, uranium. All rocks contain some uranium,
although most contain just a small amount - between 1 and 3 parts per million
(ppm) of uranium. To illustrate, fig. 1 (below) shows the concentration of uranium in ppm at the
county level in the US.

The higher the uranium level is in an area, the greater the chances are that
houses in the area have high levels of indoor radon. But studies have shown
some houses in areas with lots of uranium in the soil have low levels of indoor
radon, and other houses on uranium-poor soils have high levels of indoor radon.
Clearly, the amount of radon in a house is affected by factors in addition to
the presence of uranium in the underlying soil.

Other Factors

Some of those factors are the geology of the area, type of soil, moisture
content, and home construction. For example, homes with basements tend to have
a higher probability of radon gas exposure then those with a slab foundation.
However, even these factors do not totally explain the levels of radon in all
homes. Therefore, only testing can provide the truest measure.

Radon Potential Index

The index was constructed by weighting the above mentioned factors and
then summarizing the result. Figure 2 (below) shows the index scores for the region your city
of interest falls within. The dark purple areas have the highest risk.

More Information

More information about radon can be found by visiting the EPA's
Radon Home Page.